checkpatch: add a --strict test for comparison to true/false

Comparing to true or false is error prone.

Add tests for the various forms of (foo == true) && (false != bar)
that are only reported with --strict.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>